It can be a warning to your buds or a jest at cops for when you're walking down a sidewalk or in a park late at night with your buds, and they drive up near you and slow down, rolling by slowly to see if you're a law-breaking hooligan
<After a cop car slowly rolls by>
It's the popo in slow mo!
Someone who doesn't look fat while clothed, but secretly hides a gut
I had a locker next to that kid in gym class in high school, and trust me, he's undercover fat.
She looks hot at first, but she's just an undercover fat girl hiding beneath that sweatshirt
To drive drunk. "Good to grive" means you're drunk but you can probably make it home. It's okay to drive drunk if you don't personally know anyone who's died from it.
"Let me tell you, this man here.. He's good to grive"
"Yeah I grove home from the bar last night. It normally takes half an hour but I'd swear I made it home in five minutes."